Solvent treating of mineral oils



Jan. 5, 1943. J. J. sAvELLl ET AL SOLVENT TREATING OF MIERAL OIL Filed NOV. 22, 1940 x lll@ .n 3 lot. 143k QQ NNQLLMW III' III'

Q l NN QN lll.

PatentedJan. 5, 1943 y t 2,307,242 SOLVENT TREATINGi F MINERAL OILS `loseph J. Savelli and John M. Powers, Baytown,

Tex., assignors to Standard Oil Development Company, a corporation of Delaware Application November 22, 1940, `Serial No. 366,626 (C1. 19e-13) 9 Claims.

The present invention relates to the selective solvent extraction of mineral oils. The invention is more particularly concerned with a method for the separation and recovery of the selective solvent from the extract and ranate phases in a solvent treating process which employs as the selective solvent a substance boiling in the boiling range of the oil being extracted. In accordance with the present process the selective solvent, particularly phenol, is removed from the rainate phase and extract phase by a washing operation utilizing as the washing agent methyl alcohol and water in critical proportions in a specific series and arrangementof stages.

The customary procedure in solvent extraction processes is to employ as the selective solvent a substance whose boiling point is either above or below the boiling range of the oil being extracted in order to facilitate separation and recovery of the solvent from the extract and ralinate oils directly by distillation. For instance, it is known to extract lubricating oils with such solvents as phenol, furfural, nitrobenzene, and sulfur dioxide, all of which boil below the boiling range of the oil. Similarly, it is known to extract naphtha and kerosene stocks with sulfur dioxide which also boils below the boiling range of these oils,l But heretofore, little use has been made of phenol, furfural and nitrobenzene as selective solvents for treatment of light petroleum fractions, even though they have excellent selectivity and solvency powers, for the reason that no satisfactory and economic means of separating and recovering theseA solvents from the extract and rafnate oils has been known. We have however now dis-` covered a process employing a particular sequence of stages and critical proportions of a secondary solvent mixture whereby it is possible to economically and eiciently recover primary selective solvents from light mineral oil fractions having boiling ranges in the range of the boiling points of the primary solvents.

In accordance with our process, a light mineral oil fraction such as naphtha, kerosene, or heating oil, or the like is solvent treated in the usual manner with a primary selective solvent such as phenol, furfural or nitrobenzene under conditions to form a railinate phase and a solvent extract phase. The primary solvent after segregation of the respective phases is then separated and recovered by extracting the phases separately with a secondary solvent comprising a mixture of Water and methyl alcohol.

The process of our invention will be more clearly understood by referencev to the drawing which illustrates one modication of the same.

y and that the phenol is recovered from the separated phases by extraction with a secondary solvent comprising water and alcohol.

By means of a suitable pump, not shown, fresh oil feed is'introduced into the system through line l in which is located a heater 2. In heater 2 the feed oil is heated to a temperature of aboutA 250 F. before being introduced as' a scrubbing liquid into the phenolic water vapor scrubber 3 near its top. As the feed oil flows downwardly in countercurrent 'Contact with the upowing phenolic water Vapor discharged into scrubber 3 by means of line 4 it selectively'absorbs all or a substantial proportion of the phenol present in the vapors and rejects the water vapor which is discharged from scrubber 3 through line 5. The feed oil containing the absorbed phenol discharges from scrubber 3 through line 6 in which is located a cooler 'l for reducing the temperature of the oil tov about 815 F. before it enters the primary extraction tower 8, preferably near its center.

In primary extraction tower 8, the feed oil is countercurrently contacted with aqueous or anhydrous phenol. Although any size treat may be employed, weprefer to use about 150 per cent by volume of fresh solvent based on the feed oil at a treating temperature of about Phenol, preferably containing about 5 per cent water and which may also contain a small amount of oil,

`is introduced by means of line 9 into primary extraction tower 8 near its top. For purpose of producing oil reflux in the lower section of the primary extraction tower, methyl alcohol and phenolic water, introduced through lines Il and I2, respectively, are mixed and then injected into the lower half of tower S at desired points by means of distributing lines l which are in communication with lines Il and l2. This alcoholwater mixture may vary considerably in quantity and composition and still produce good results. In general, we prefer to use as the precipitating agent a 1:1 mixture of methyl alcohol and water which may or may not contain a small percentage of phenol.

The raffinate or oil phase is withdrawn from the top of primary extraction tower 8 by means of line I3 and introduced into secondary, raffinate extraction tower I4 where it is contacted countercurrently with a secondary solvent comprising methyl alcohol and water for removal and recovery of the phenol. Although the alcohol and water may be introduced as a 1 :1 mixture through line I5, we prefer to introduce these constituents separately. The alcohol preferably alone or in admixture with a small amount of water is introduced through line I5 while the water is introduced through line I6 at a point higher in the tower. This mode of operation obviates the necessitv of additional equipment for water washing. The desolventized ranate oil is discharged from the top of secondary extraction tower I4 through line I1 and is passed to storage or sub jected to further treatment as desired.

The extract phases comprising methyl alcohol, water and phenol as well as small amounts of dissolved or suspended oil withdrawn from secondary extraction tower I4 by means of line I9 and from secondary extraction tower I8 by means of line 28 are combined with the primary extract withdrawn from primary extraction tower 8 through line 2 I. The resultant mixture is passed through incorporator 22 and heater 23 in line 2I and introduced into extract settler 24. Incorporator 22 thoroughly mixes the primary extract phase with the secondary extract phase and facilitates the precipitation of an oil phase as well as a redistribution of the phenol between the oil phase and the alcohol-water phase. Raising the temperature of the mixture to about 150 F., by means of heater 23 facilitates a more rapid separation of the precipitated oil phase from the alcohol-water phase.

The precipitated extract oil which separates from the alcohol-water phase in extract settler 24 is passed through line 25 into secondary, ex`

tract extraction tower I8 wherein itis contacted countercurrently rst with a methyl alcoholphenolic water mixture introduced through line 26 and then with methyl alcohol which is introduced by means of line 21. The extract is finally treated with substantially solvent-free water which is injected through line 28. A temperaf ture of approximately 85 F. is employed in secondary extraction tower I8. The desolventized extract oil is withdrawn from secondary extraction tower I8 by means of line 29 and is passed to storage or treated further as desired.

The water-alcohol-phenol phase withdrawn from extract settler 24 by means of line 30 is passed through heater 3I in line 38, wherein its temperature is elevated to approximately 200 F. before the mixture enters distillation unit 32. In distillation unit 32, the methyl alcohol is separated as a distillate from the water and phenol. This alcohol distillate is withdrawn from the unit through line 33 and cooled to approximately 85 F. by means of cooler 34. The alcohol recovered in this manner is then recycled to the extraction zones by means of lines II, I5, 26 and 21 which are in communication with line 33. When necessary, make-up alcohol is introduced into the system through line 35.

The phenol-water mixture withdrawn as a residuum from distillation unit 32 by means of line 38 is passed through cooler 31 wherein its temperature is reduced to approximately 85 F. before the mixture is introduced into phenolic water settler 38. In this settler, the phenolwater mixture is separated into two liquid phases. The upper layer is predominantly water with some phenol while the lower layer is predominantly phenol with some water and a very small percentage of oil. The upper layer of phenolic water is withdrawn from settler 38 through line 39 and is recycled to primary extraction tower 8, by means of lines I2 and I Il, and to secondary extraction tower I8, by means of lines 40 and 26. The greater part of the recycle phenolic water goes to the latter tower.

The lower layer of aqueous phenol withdrawn from settler 38 by means of line 4I is passed through a heater 42 and introduced into distillation unit 43. In distillation unit 43, the aqueous phenol is separated by distillation into a distillate comprising water containing phenol in an amount approximately equivalent to the waterphenol azeotrope and a residuum comprising anhydrous phenol with a small percentage of oil.

`The recovered phenol withdrawn as a residuum from Vdistillation unit 43 through line 44 is cooled to approximately 85"4 F. by means of cooler 45 and recycled to primary extraction tower 8 through line 9. When necessary, make-up phenol may be introduced into the system by means of line 45. In some operations, for example in the extraction of mineral oils with aqueous phenol,

it may be preferable to withdraw aqueous rather than anhydrous phenol as a residuum from distillation unit 43. 'Ihis may be readily accomplished by proper control of temperature and pressure conditions in distillation unit 43. Generally, the quantity of water remaining in the recovered phenol will not be greater than about 5 per cent. However, if desired, the water concentration may be as high as 15 per cent.

The water-phenol azeotrope distillate separated in distillation unit 43 is passed as a vapor through line 4 into phenolic water vapor scrubber 3 wherein the phenol is recovered in the manner already described and the water vapor is discharged from the scrubber through line 5. A cooler 41 is located in line 5, which condenses this water vapor and cools the liquid to approximately 85 F. The cool liquid water discharges into settler 48 wherein any entrained charge or scrubbing oil separates and is recovered from the water. 'I'he recovered oil is returned to the charge oil flowing through line 6 by means of line 49. The recovered water withdrawn from settler 48 by means of line 58 is recycled to primary extraction tower 8 by means of lines 5I and 9 and to secondary extraction towers I4 and I8 by means of lines I8 and 28, respectively. If desired, a portion of this recovered water may be passed from line 50 through line 53 to line 33 wherein it is mixed with the methyl alcohol being charged to secondary extraction towers I4 and I 8. When the oil is extracted with anhydrous phenol, no water is recycled through line 5I to the primary extraction tower 8. Make-up water may be added to the system by means of line 52.

When the charge oil introduced into scrubber 3 through line I is insuicient in quantity to completely recover the phenol from the water vapor, an auxiliary scrubber may be superimposed in line 5 ahead of cooler 41. The scrubbing medium employed in the auxiliary scrubber should preferably consist of an oil having a higher boiling range than that of the phenol so that distillation means could be employed for separating and recovering the phenol from the scrubbing medium. When operating with an auxiliary scrubber of this type, the oil separated in settler 48 would be directed to the auxiliary scrubbingmedium distillation unit instead of being introduced into line 6 to be mixed with the feed oil going to the primary extraction tower 8.

The present invention may be widely varied. The process may be readily adapted for the removal of phenol from the respective phases secured in the solvent treatment of any feed oil. lt is however especially suitable for the recovery of phenol from the respective phases secured in the phenol treatment of relatively low boiling petroleum oils.

We have found that water alone is not satisfactory as a secondary solvent for the reason that equilibrium conditions for a water-oil-primary solvent system is not sufficiently favorable for an economic separation of the primary solvent from the oil in this manner. On the other hand, methyl alcohol'is too miscible with both the oil and the primary solvent to be used economically as a secondary solvent for the separation of these two constituents. However, we have found a suitable secondary solvent in a mixture comprising water and methyl alcohol, the

concentration of the alcohol in the mixture being =f in the range between about 30 and about 70 per cent by volume and varying depending upon whether a batch or countercurrent operation is employed. By using suitable quantities of this secondary solvent mixture, we have found it possible to remove substantially completely the primary solvent from the extract and raffinate oils. The resulting extract and raflinate oils contain a small amount `of alcohol which is readily removed by a subsecuent water wash.

Distillation means are employed for separating the primary solvent from the constituents of the secondary solvent. In general, the operation involves removal as distillates the alcohol first, then the water r an azeotropic mixture of the water and the primary solvent, leaving as a residuum the primary solvent which usually contains from traces to a few per cent of oil. The alcohol, water, and primary solvent segregated in this manner are then returned to the extraction process as recycle. The residual oil in the recovered primary solvent is suliciently low in con centration as not to abate appreciably the se lectivity or solvency power of the primary solvent.

Where azeotropic mixtures are not encountered,

the distillation operation involves only simple fractionation. When encountered.y the azeotropic mixtures are subjected to a scrubbing in the vapor state with an oil liquid, preferably the charge to the primary extraction tower, which selectively dissolves the primary solvent and rejects the water vapor, thereby effecting recovery of the solvent from the azeotrope. While the quantities of alcohol and water used to separate the phenol from the oil may vary over wide limits with satis-l factory results, we have found itr advantageous to employ approximately 21 parts of water and 11 parts of alcohol to effect a separation of 1 part of extract oil from 7 parts of phenol. It has been found that the phenol can be substantially completely removed from the raffinate oil by employing approximately per cent treats, based on the wet raffinate, for both the alcohol and the water in accordance with this method.

In order to further illustrate the invention the following examples are presented and are not to be construed as limiting the scope of our invention in any manner whatsoever. These examples illustrate the type of products obtainable from a subjected to a secondary'extraction for removal 1 kerosene stock when treated with aqueous phenol in accordance with the method of our process;

EXAMPLE 1 Kerosene boiling in the range from about 400 F. to 590 F. and containing 23.5 per cent aromatics by volume was countercurrently treated with 150 per cent of 95V per cent fresh aqueous phenol. Five stripping and three reflux stages were employed, each reflux stage receiving a 12.5 per cent injection (based on the phenol-free oil charge) of a 1:1 mixture of methyl alcohol and water. The extraction was conducted at substantially atmospheric pressure and at a vtemperatureof about F.

The primary extract phase obtained in the above operation was subsequently subjected to a five-stage secondary extraction for the separation of the phenol and extract oil, using as the secondary solvent a mixture comprising 73 per cent water and 27 per cent methyl alcohol and employing a 300 per cent treat. The desolventized extract oil was then given a final water wash and analyzed for phenols. The phenol content of the extract oil was found to be 0.005 per cent. The primary raffinate phase was also similarly of the phenqol. j

Of the hydrocarbon oil charged, 90.7 per cent was recovered as extract and raffinate oils. The apparent 9.3 per cent loss obtained is due primarily to aromatic constituents which remained dissolved in thel recovered phenol. Analysis of the extract oil phase showed it to comprise 55 per cent aromatics. The improvement in the quality of the kerosene stock effected by means of our extraction process with phenol as the primary solvent will be noted from a comparison of the following data:

TABLE I (.Jstle Ratliuate Extract Gravity, 30. 4 43. 4 25. 5 Ring No.l 17 88 I. P. T. smoke point, mm 38 This test indicates burning quality of oil; the higher the value, the better the quality.

EXAlVIPLE 2 Another portion of the same kerosene stock employed in the experiment described under Example 1 was countercurrently extracted with recovered per cent aqueous phenol, using a 150 per cent treat and employing 7 stripping stages and 7 reflux stages. A quantity of a 1:1 mixture of methyl alcohol and water amounting to 20` per cent of the phenol-free oil charge was injected in each reflux stage. The extract and raiinate phases obtained from this treat were subsequently desolventized separately by subjecting each of them to a secondary 5 stage extraction, employing as the secondary solvent a mixture comprising about equal parts of methyl alcohol and water. A final water wash was employed to remove the alcohol dissolved in the oil. A yield of approximately 75 per cent raffinate oil and 25 per cent extract oil was obtained. The extract oil contained aromatics in a concentration of about 80 per cent. The raffinate oil contained only about 3 per cent aromatics and had the following properties: A. P. I. gravity, 42.8; ring number, '78; I. P. T. smoke point, 31 mm.

EXAMPLES Batch extraction operations were conducted using as charge oils heavy naphtha and kerosene' stocks having varying aromatic contents and employing solvents comprising mixtures of (1) phenol and water, (2) phenol and alcohol, and (3) phenol, alcohol and water. These operations were conducted at room temperature which ranged between 75 and 85 F.

Aqueous phenol solutions of 90 to 95 per cent strength were employed as the primary solvent for separating heavy naphtha and kerosene stocks into their more aromatic and more parafnic constituents. In one series, the oils were treated at 75 F. with 160 per cent by volume of 95 per cent strength aqueous phenol while in another series, the oils were given a 100 per cent treat with 90 per cent strength aqueous phenol at a temperature of 85 F. The data obtained in these operations are given in Tables II and III below.

tower, but that it is not capable of concentrating the aromatics in the extract oil to a value higher than about per cent. The oils comprising more than about 50 per cent aromatics are completely miscible in 90-95 per cent strength aqueous phenol at room temperature C-85 FJ. This inability to concentrate the aromatics to a value greater than about 50 per cent is an undesirable feature. In commercial operations it is desirable to have the primary solvent concentrate the aromatics to a value above about '70 per cent, preferably per cent or 90 per cent.

Operations in which the solvent power and selectivity of the to 95 per cent aqueous phenol primary solvent was modified in a countercurrent extraction process, by injecting a mixture of water and methyl alcohol at selected points in the lower or extraction section of the tower was conducted. The operations consisted of making two series of batch extractions on heavy naphtha and kerosene charge stocks of varying aromatic content. In one series, the solvent consisted of a 5:1:2 mixture of phenol, water and methyl a1co hol, respectively. In the other series, a l.5:1:2

TABLE II Kerosene stocks extracted with aqueous phenol TREAT-160% TEMPERATURE-75 F.

Oil charge volumes 100 100 100 100 100 100 percent.- 97. 5 83.2 69. 3 62. 4 55. 3 41.2 27.0 do 2. 5 26. 8 30. 7 37. 6 44. 7 58. 8 73. 0 Refractive index at 75 F 1.4422 1.5132 Anhydrous phenol. vo1umes 152 152 152 152 152 152 152 Water do 8 8 8 8 8 8 8 Phases separating on settling Upper Lower Upper Lower Upper Lower Upper Lower Upper Lower Upper Lower Upper Lower 2 hours layer layer layer layer layer layer layer layer layer layer layer layer layer layer Volumes 86. 0 174. 0 74. 8 185. 2 58. 0 202. 0 50. 0 210. 0 Parailins. percent.- 94. 6 9. 3 87. 0 9.8 80. 4 ll. 2 75.8 l1. 6 Aromatics d0 0.9 l. 0 7. 0 6.1 13. 1 11. 4 16. 7 14. 0 Phenol and water do 4. 5 89. 7 6.0 84.1 6. 5 77. 4 7. 5 74. 4 Properties of desolventized oil (primary solvent removed by treatment with methyl alcohol- Water secondary solvent):

Paraiiins pereent-. 99. 0 90. 4 92. 5 61. 6 86. 0 49. Aromatics do 1.0 9. 6 7. 5 38. 4 14. 0 50. Refractive index at 75 F 1. 4410 1.4475 1.4542

TABLE III Heavy naphtha stocks extracted with 90% aque oas phenol TREAT-100% TEMPERATURE-85F.

Mixture 1 2 3 4 Composition:

il charge volumes-- 100 100 100 100 Parains .percent 87. 6 79. 2 s2, 4 33, 0 Aromatics 12. 4 20. 8 37.6 67, 0

Anhydrous phenol.- vo1umes 90 90 90 90 Water d0.- 10 10 10 10 Phases separating on settling 2 hours Upper Lower Upper Lower Upper Lower Upper Lower layer layer layer layer layer layer layer layer Quantity volumes.. 83 117 78 Composition:

percent.. 81. 0 17. 3 78. 4 8. 0 5. 0 13. 7 11. 0 77. 7 7. 9 Properties of desolven by treatment with methyl alcohol-water secondary solvent Parans percent 91. 0 77. 8 85. 0 Aromatics d 0 2 l5. 0 Refractive index at 68 F 1. 4269 It is to be noted that a 90-95 per cent aqueous phenol is a good solvent for aromatics in the stripping zone of a countercurrent extraction 75V ations a mixture of these same components was employed asthe solvent. The data obtained in these operre-given in Tables IV and V.

TABLE IV Kerosene stocks extracted with a :1 :2 mixture of phenol, water and methyl alcohol TREAT-160% TEMPERATURE-83 F.

Mixture 1 2 3 4 5 Composition:

Oil charge volumes-. 100 100 100 100 100 Paran percent-- 97. 5 83. 2 62. 4 41. 2 27. 0 Aromatics do 2. 5 26. 8 37. 6 58. 8 73. 0 Refractive index at 75 F-- 1.4422 1. 5132 Anhydrous phenol. .volumes 100 100 100 100 100 Water do-- 20 20 20 20 Methyl alcohol do 40 4U 40 40 Phases separating on settling Upper Lower Upper Lower Upper Lower Upper Lower Upper Lower 2 hours layer layer layer layer layer layer layer layer layer layer Quantity volumes.. 96 164 88 172 180 196 52 208 Composition:

Parains .percent-- 95.9 3.2 86.4 4 3 60 0 4 6 49.4 4 4 32 7 4 8 Aromatics -..do.-. 1.2 0.9 9.5 4 8 23 10 7 40.6 16 8 49.2 22 8 Phenol, alcohol, and

wa er do. 2.9 95.9 4.1 90 9 7 0 86 7 10.0 78 8 18 l 72 Properties of desolventized oil (primary solvent removed by treatment with a methyl alcohol-water secondary solvent):

Parailns .percent--- 99 78 90 47.4 64.5 29.8 55.0 20 6 40.0 17 4 Aromatics do.. 1 22 10 52.6 35.5 70.2 45.0 79 4 60.0 82 6 Refractive index at F I. 4412 1. 4502 1. 4653 1. 4857 l TABLE V Heavy naphtha stocks lextracted with a 1.5:'1 :2 mixture of phenol, water and methyl alcohol TREAT-240% TEMPERATURE- r.

Mixture 1 2 3 4 Composition:

Oil charge volumes.- 100 10o 100 Paramus percent.- 45.6 28. 8 22. 0 12 Arnmatira dn 54. 4 7l. 2 78. 0 88 Refractive index at 75 F 1. 4858 Anhydrous phenol volumes-- 80. 0 80.0 80.0 so. o Water do--. 53.6 53. 6 53. 6 53. 6 Methyl alcohol -.d0.- 106.4 106. 4 106.4 106.4

Phases separating on settling 2 hours Upper Lower Upper Lower Upper Lower Upper Lower layer layer layer layer layer layer layer layer Quantity volumes-. 78.0 262.0 75 2 264.8 74.0 266.0 78,0 252,0 Composition:

Pai-affine percent-- 48. 2 3. 1 29. 4 2. 6 60. 5 2. 5 9. 7 1. 7 Arm-native do. 44. 6 7. 5 55. 7 11. 1 20. 6 12. 5 61. 3 15. 3 Phenol, water, and methyl alcohol --do.- 7. 2 89- 4 14. 9 86. 3 18. 9 85. 0 29. o sa, o Properties of desolventized oil (primary solvent removed by methyl alcohol-water secondary solvent):

Parains percent-- 51. 8 29. 0 34. 5 18. 8 23. 5 l7. 0 13. 8 10 3 Aromatics 0.--. 48. 2 71- 0 65. 5 81. 2 76. 5 83. 0 86. 2 89 7 Refractive index at 75 F 1. 4530 l. 4672 1. 4746 1. 4842 Itis to be noted that both of the solvent nuxtures lOperatlons were also conducted 1n Whlch exemployed exhibit the ability to progressively tract oil was precipitated from solution in phenol concentrate aromatics in the extract oil from 50 by use of secondary solvents. In these operavery low values to very high values. Hence, it is tions a mixture of Water and methyl alcohol was obvious that the injection of a water-alcohol used as a secondary solvent for precipitating exmixture at selected points in the extraction sectract oil from the phenol solution. It is apparent tion of the primary tower is very desirable as a that neither the Water nor the alcohol taken sepmeans for modifying the solvent power and 55 arately are capable of effecting suchaseparation.

selectivity of phenol. The data obtained are given below in Table VI.

TABLE VI Precipitation of kerosene extract on from, phenol solutzon by use of a secondary solvent 1:2 mixture Secondary solvent of water and methyl f Mixture aggllft Water at 74 F. Methyl alcohol ai 74 r.

Composition of mixture:

Extract oil (73% aromatles) volumes.. 20 20 20 20 20 20 20 20 20 20 20 20 20 Anhydrous phenol 110..-. 20 16 100 100 100 100 100 100 100 100 100 100 100 Water added do 4 10. 7 10 20 30 40 62 Methyl alcohol added -.do 8 21. 3 0 10 20 40 80 130 Natrl'e and amount of phases separating after l. hour y se mg:

Oil-rich layer volumes 10.4 l5 0 0' Emu1 0 0 0 0 0 0 o 0 Phenol-rich layer fin 140 smed 1144 l 142 120 130 140 160 200 250 Water-rich layer.. do 0 0 16 i 38 Methyl alcohol-rich layer do 0 0 Phenol-water-methylalcohol-richlayer.-. do 41.6 53 u 1 Slightly emulsifled.

Although our invention has been described by' m"water and methyl alcohol under conditions to reference to a particular embodiment thereof, it

is obvious that many modications may be employed without departing from the spirit and scope of the invention. Hence, the invention is not to be construed as limited in any manner except by the appended claims.

We claim:

l. In a selective solvent extraction process for the segregation of an oil into its relatively more paraiinic and relatively more aromatic constituents which employs as the primary selective solvent a substance boiling in the boiling range of the oil being extracted and wherein the more paraiiinic constituents are separated as an oil phase containing dissolved therein a. small amount of the solvent and the more aromatic constituents are separated with the solvent phase in which they are dissolved, the means of separating and recovering the primary selective solvent from the oil constituents in said oil phase and in said solvent phase which comprises subjecting these phases separately to a secondary solvent extraction with a mixture of water and methyl alcohol which selectively dissolves the primary solvent and rejects the oil, washing both the rejected rafnate oil and rejected extracted oil with water, combining the primary extract phase with the extract phases of said secondary solvent extractions and water washings, heating the resultant extract phase mixture to a separation-accelerating temperature, separating the water-methyl alcohol-primary solvent phase from contact with the rejected oil, and segregating the water-methyl alcohol-primary solvent phase'by distillation means into an alcohol component which is recycled to the extraction zones and into a water-primary solvent component which is cooled and separated by settling into its two constituents which are then each recycled to the extraction zones.

2. A process for segregating a mineral oil into its relatively more aromatic and relatively more parainic constituents which comprises contacting said mineral oil with a primary selective solvent, separating a raffinate phase comprising the more parafnic constituents with some dissolved solvent and an extract phase comprising the primary selective solvent and the more aromatic constituents, subjecting said raii'inate phase and said extract phase separately to secondary solvent extractions with mixtures of water and methyl alcohol which selectively dissolve the primary solvent and reject the oil, washing both the rejected raffinate oil and rejected extracted oil with water, combining the primary extract phase with the extract phases of said secondaryV solvent extractions and water washings, heating the resultant extract phase mixture to a separation-accelerating temperature, separating the water-methyl alcohol-primary solvent phase from contact with the rejected oil, and segregating the water-methyl alcohol-primary solvent phase into its component parts by known distillation means.

3. Improved solvent treating process comprising contacting a feed oil in an initial stage with a solvent selected from the class of solvents having a preferential selectivity for the relatively more aromatic type constituents as compared to the relatively more parainic type constituents under conditions to form a solvent extract phase and a rainate phase, separating the raflinate phase and contacting the same in a secondary produce a solvent-free 'raffinate and a secondary extract, removing the secondary extract and combining the same with the extract removed from the primary stage, passing the combined extracts to a separation zone operated under conditions to separate a phase containing the extract and a substantially extract-free solvent phase, passing the phase containing the extract to a tertiary stage and contacting the same in said tertiary stage with a solvent comprising water and methyl alcohol under conditions to separate from said tertiary stage a solvent-free extract and a solvent extract phase, combining said solvent extract phase with the extract removed from said primary stage and said secondary stage prior to introducing said extract into said separation zone.

4. Process in accordance with claim 3 in which said solvent removed from said'separation zone is passed to a distillation zone, wherein a separation is made between the methyl alcohol and the primary solvent and in which said methyl alcohol is recycled to said secondary and said tertiary stage and said primary solvent is recycled to said primary stage.

5. Process in accordance with claim 3 in which the concentration of the methyl alcohol in the solvent introduced into said secondary stage and into said tertiary stage is in the range from about 30 to 70 per cent.

6. Process as defined by claim 3 in which the water and alcohol are introduced into said secondary and into said tertiary stage in a manner stage with a secondary solvent consisting of that the feed to said secondary and said tertiary stage rst contacts the methyl alcohol.

7. In a selective solvent extraction process for the segregation of a mineral oil into its relatively more parafnic and relatively more aromatic constituents which employs as the primary selective solvent a substance boiling in the boiling range of the oil being extracted the steps comprising in combination introducing the mineral oil charge into a primary extraction zone, the upper portion of which serves as stripping section and the lower portion of which serves as reux section, countercurrently contacting said mineral oil with a primary solvent introduced into the stripping section of said primary extraction zone whereby a primary rafnate phase and a. primary extract phase are formed, introducing into the reflux section of said primary extraction zone an agent adapted to modify the selectivity of the primary solvent as between the more paraflinic and the more aromatic constituents, separating the primary raiinate phase and contacting the same in a secondary stage with a secondary solvent consisting of water and methyl alcohol under conditions to produce a solventfree raffinate and a secondary extract, removing the secondary extract and combining the same with the extract removed from the primary stage, passing the combined extracts to a separation zone operated under conditions to separate a phase containing the extract oil and a substantially oil-free solvent phase, passing the phase containing the extract oil to a tertiary stage and contacting the same in said tertiary stage with a solvent consisting of water and methyl alcohol under conditions to separate from said tertiary stage a solvent-free extract oil phase and a substantially oil-free mixed solvent phase, combining said mixed solvent phase with the extracts removed from said primary stage and said secondary stage prior to introducing said extracts into said separation Zone, segregating the Watermethyl alcohol-primary solvent phase removed from said separation zone substantially into its components, and recycling said components to the process.

8. Process in accordance with claim 7 in which the primary solvent comprises 90 per cent to 100 per cent phenol and 10 per cent to 0 per cent water, the modifying agent comprises a mixture containing about two volumes of methyl alcohol and one volume of Water, and the ratio of said modifying agent to said primary solvent entering the primary extraction zone is in the range between about 0.5 to 1.0 and about 2.0 to 1.0.

9. Process in accordance with claim 7 in which the Water-methyl alcohol-primary solvent mixture removed from said separation zone is passed to a distillation zone wherein a substantially complete separation is made between methyl a1- eohol, water and the primary solvent, and in which said primary solvent is recycled to the primary extraction zone and the methyl alcohol and Water are recycled to the reflux section of the 10 primary extraction zone and to the secondary and tertiary extraction zones.

JOSEPH J. SAVELLI. JOHN M. POWERS. 

